Portable oxygen concentrator



FIG. 1 is a perspective view of a portable oxygen concentrator showing our new design;

FIG. 2 is a top plan view thereof;

FIG. 3 is a rear elevation view thereof;

FIG. 4 is a first side elevation view thereof; and,

FIG. 5 is a second side elevation view thereof.

The broken line showing in FIGS. 1 and 2 is for illustrative purposes only and forms no part of the claimed design. 

The ornamental design for a portable oxygen concentrator, as shown. 